Huffington Post published a story Wednesday afternoon which includes some choice quotes from former Clinton campaign staffers. The overall message of the piece is that this election was winnable for Clinton if she and her campaign hadn’t made a series of mistakes, especially in the closing days. The reason for those mistakes was overconfidence or, as one staffers says, arrogance:

“It was arrogance, arrogance that they were going to win. That this was all wrapped up,” a senior battleground state operative told The Huffington Post.

Several theories have been proffered to explain just what went wrong for the Clinton campaign in an election that virtually everyone expected the Democratic nominee to win. But lost in the discussion is a simple explanation, one that was re-emphasized to HuffPost in interviews with several high-ranking officials and state-based organizers: The Clinton campaign was harmed by its own neglect.

That neglect was largely based on polling which showed Clinton up 6-7 points in Wisconsin (for instance). But even when the Clinton team began to sense some vulnerabilities in rust belt states they decided they could manage it with mind games:

A senior official from Clinton’s campaign noted that they did have a large staff presence in Michigan and Wisconsin (200 and 180 people respectively) while also stressing that one of the reasons they didn’t do more was, in part, because of psychological games they were playing with the Trump campaign. They recognized that Michigan, for example, was a vulnerable state and felt that if they could keep Trump away ― by acting overly confident about their chances ― they would win it by a small margin and with a marginal resource allocation.

But the mind games and pretend confidence didn’t work. What did work was…well, work. A report published Sunday by NBC News notes that in the last 100 days of the campaign Trump simply outworked Clinton in the states that were critical to his success:

Trump out-campaigned Clinton by 30 percent in Florida, winning by 1.3 points a state that had gone Democratic in 2008 and 2012.

In Pennsylvania, Trump made 23 percent more visits and won the previously blue state by 1.2 points.

The biggest disparity came in Ohio, where Clinton made 17 stops and Trump made 26. He won the state by more than 8 points. In North Carolina, Clinton made 16 stops as Trump made 23, and he took the state by a little under 4 points.

And in what may prove to be this cycle’s most stunning 11th hour upset, Michigan hosted Trump 13 times in the last 100 days. Clinton visited just six times in comparison and, as of Sunday, was behind Trump by 47.3 to 47.6 percent.

Back when Trump was making this mad dash around the country there were left-leaning journalists and Republican polling experts saying it made no sense. From Talking Points Memo:

Trailing in the polls, the real estate mogul first announced last week that he planned to accelerate his campaign schedule in the race’s final days in order to take the case directly to voters. His team has promoted this jam-packed itinerary as proof that he is a tireless, spirited politician.

Trump has “the most active campaign schedule of the two candidates by far,” campaign manager Kellyanne Conway told NBC’s “Today Show.”

Veteran campaign strategists still aren’t buying it.

“Do I see the strategy behind it? No,” Republican pollster Ed Goeas told TPM.

Of course it probably didn’t help that Hillary came down with pneumonia in mid-September. A doctor interviewed by the Washington Post’s Chris Cillizza suggested recovering from this type of infection could take, “four to six weeks to feel back to normal, in terms of stamina.” At a minimum then, this may have been dogging Clinton into early October and maybe even until later in the month.

That aside, Hillary’s team was overconfident of success and Trump’s team engaged in an exhausting, last-minute strategy of direct appeal to voters which, while not offering a guarantee of success, gave them their best chance. In the end, his team’s hard work trumped her team’s arrogance.